Adjustable speed fluid actuated servomotor



Patented Feb. 20, 1951 um'rso srAjrEs PATENT OFFICE 1 v we Sidney Lockwood Gillespie, Rockford, m, assignor to Woodward Governor Company, Rockford,

111., a corporation of Illinois Original application May 3, 1945, Serial No.

591,809, now Patent No. 2,495,284, dated Febrnary l, 1950. Divided and this application November l, 1946, Serial No. 70!;225

Claimu (Cl. 121-41) This invention relates to hydraulic servos and more particularly to the manner of controlling the flow of pressure fluid thereto to regulate the rate of change of position or the element actuated by the servo.

One object is to interpose in the fluid supply line leading to the servo a novel means for passing pressure fluid intermittently.

The invention also resides in the novel structural character of the intermittently acting means and to the manner of its adjustment for diilerent average rates of fluid flow.

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings, in which Figure 1 is a schematic cross-sectional and hydraulic circuit diagram of a fluid servo embodying-the novel features of the present invention.

Figs. 2, 3, 4, and 5 are fragmentary sectional views taken respectively along the lines 2-2,

. 3-3. 4-4. and 5-5 of Fig. 1.

In the drawings, the invention is shown for purposes or illustration embodied in a servo actuator for effecting speed adjustment 01' a governor ill. The latter includes fiyballs ll pivoted on a ball head l2 which is rotated in unison with the governed prime mover. Centrifugal force on the flyballs is balanced against the stress of a compression type speeder spring l3 which is adjusted for different speed settings by movement of an abutment |4. Herein. this abutment or speed adjusting element constitutes the piston of an hydraulic actuator i5 including a cylinder IS in which the piston reciprocates. The piston is urged upwardly by a compression spring i1 and is moved downwardly by the admission of pressure fluid to the cylinder from a suitable source whichmay comprise a pump l8 driven in unison with the governor ill and associated with a suitable by-pass valve (not shown) to maintain the pressure in the pump outlet l9 substantially constant.

The flow of fluid to the servo actuator i5 is through a passage 42 to which fluid is supplied under the control of a valve comprising a land 2| on a reciprocable stem 22 and a cooperating port 23in a sleeve 24. The latter is continuously rotated from the ball head l2 through a gear 25 meshing with a gear 26 fast on the lower end of the sleeve and journaled on a stud 21. The upper end portion of the sleeve 24 is journaled in a bore 23 in the governor casing 43 and in a counter-.

bored portion of a bushing 30 having a shoulder against which the sleeve 24 is urged by a spring v2 23. Angular adjustment of the bushing is permitted by a slot 34 formed in a. flange 33 of the bushing and receiving a screw 35 by which the bushing may be clamped in adjusted position.

The fluid supply line H leads to the interior of the sleeve 24 through a passage 3| which registers continuously with a hole 32 in the bushing 30. Once during each revolution of the sleeve 24, a longitudinally elongated slot 36 in the exterior of the sleeve 24 is brough t into registry with the hole 32. During a part of such registratlon, the slot 36 also registers with a port 31 which is angularly spaced from the passage 3| and the port 32 as shown in Fig. 4. The port 31 communicates through a passage 38 and a port 33 with an annular groove 40 around the sleeve 24. A hole 4| leads from this groove to the interior oi the sleeve 24 above the valve land 2|.

It will thus be seen that fluid from the supply line will flow to the valve chamber during that portion oi each revolution 01' the sleeve in which the sleeve slot 36 is in registry with both the bushing hole 32 and the port 31 as shown in Fig. 4. By adjusting the bushing 3|] angularly, the amount of such simultaneous registration may be increased or. decreased as desired thereby varying the average rate oi! fluid flow through the central valve 20 when the latter is open. Very slow rates 01' flow may thus be obtained even though the fluid passages are of relatively large size and not subject to clogging.

The stem 22 of the valve 20 projects from the upper end of the sleeve 24 and is pivotally connected to one end of a lever 44 fulcrumed on a floating pin 45 and urged upwardly by springs 53 and 54 and connected at its other end to a link 46. The upper end of the latter is pivotally connected intermediate the ends of a lever 41 fulcrumed at 48 and pivotally connected at 49 to the outer end of a rod 50 on the servo actuator piston |4. Herein, the position of the fulcrum 45 is changed selectively according to the desired adjustment or the piston i4 by energizing a plurality oi solenoids 5| in difierent combinations. The armatures 01' these bear at spaced points against a plate 52 constituting a diiferential lever and carrying the fulcrum 45 intermediate these points. The spring 54 bears upwardly on the plate 52 to hold the latter against the solenoid armatures.

When the system is in equilibrium, the parts will be positioned as shown in Fig. l, the servo piston I4 occupying a position corresponding to the position of the fulcrum 45. Now. if the fulcrum 45 is lowered, the valve land 2| will be moved correspondingly, and fluid from the sup- 3 ply line [9 will flow into the passage 42 and the servo cylinder I each time the slot 86 comes into registry simultaneously with the hole 82 and the port 31. The resulting downward motion of the servo piston i4 is imparted to th lever 44 which swings about the fulcrum l5 and raises the valve land. By virtue of this follow-up action, the valve becomes closed when the servo piston reaches a position corresponding to the new position of the fulcrum point 45. In the motion of the servo piston to its new position, the speeder spring is compressed and the speed setting of the governor, and, therefore, the speed of the controlled prime mover are increased correspondingly. The rate of this speed increase is, it will be observed, limited by the flow of fluid to the servo cylinder which takes place intermittently and, therefore, at an average rate determined by the selected adjustment of the bushing.

Speed decreasing adjustment of the servo ll takes place when the position of the fulcrum I! is raised to open the valve 20 and allow fluid from the servo cylinder to escape to the drain through the lower end of the sleeve 24. In this case, however, the intermittently opened valve is by-passed so that the rate of decrease in the speed adjustment is not limited.

This application is a division of my copending application Serial No. 591,809, flied May 3, 1945, nowPatent No. 2,496,284.

I claim as my invention:

1. The combination of a servo energized by the flow of pressure fluid thereto comprising means defining a bore, a sleeve continuously rotating in said bore, a plunger slidable in said sleeve and cooperating with a port in the sleeve to form a valve, and means providing a fluid supply passage leading to said servo through said valve and including ports in said bore and said rotating sleeve adapted to register during part of each revolution of the sleeve and to remain out of register during the remainder of the revolution.

2. The combination of a servo energized by the flow of pressure fluid thereto comprising means defining a bore, a plunger slidable in said bore and cooperating with a port in the bore to form a valve, and means providing a fluid suppl passage leading to said servo through said valve and including two parts continuously rotated relative to each other and having ports which register during part of each revolution to permit of fluid flow through said passage and which remain out a sleeve rotatable in said bore, a plunger slidable in said sleeve and cooperating with a port therein to form a valve which is opened and closed by shifting said plunger and sleeve relative to each other axially, and means providing a fluid passage leading into said sleeve at one end of said plunger including ports in said bore and sleeve adapted to register with each other during part of each revolution of the sleeve and to remain out of register during the remainder of the revolution.

4. The combination, of, means defining a bore, a sleeve rotatable in said bore, a plunger slidable in said sleeve and cooperating with a port therein to form a valve which is opened and closed by shifting said plunger and sleeve relative to each other axially, means providing a fluid passage leading into said sleeve at one end of said plunger including ports in said bore and sleeve adapted to register with each other during part of each revolution of the sleeve and to remain out of register during the remainder of the revolution, and a bushing surrounding said sleeve and one of said ports and angularly adjustable to vary the effective area of such port.

5. A valve for controlling the flow of fluid under pressure comprising means defining a cylindrical bore having a flrst and second port opening therein and spaced apart axially of the bore, a cylindrical bushing projecting into one end of said bore across said first port and having a hole therethrough registering with and smaller than the flrst port, means for holding said bushing in different positions of angular adjustment, and a rotary shaft journaled in said bushing and said bore and having a recess adapted to register with both said hole and said second port during part of each revolution of the shaft, said shaft closing said hole and said second port during the remainder of the revolution.

SIDNEY LOCKWOOD GILLESPIE.

REFERENCES CITED The following references are of record in the flle of this patent:

UNITED STATES PATENTS 

